1. Field of the Invention
The present invention relates to a spring forming apparatus, and more specifically the spring forming apparatus comprising a wire feeding unit by which a wire as a spring material is forcibly fed with utilization of at least a pair of wire feeding rollers and fed into a wire working region through a quill, and a plurality of separate wire working units by which the wire fed from the wire feeder unit is bent, coiled and cut to obtain a spring.
2. Description of Related Art
There have been proposed various types of spring forming apparatuses. Some of them will be described below:
(1) JP-B2-4-734 discloses a spring forming apparatus in which a plurality of tools which movable between an advanced position of wire working and a retreated position, the tools being arranged so as to surround a quill through which a wire to be worked is fed out to the wire working position. The spring forming apparatus includes two large gears which drive a forming tool and a cutting tool and which are arranged in parallel to each other so as to be rotatable around the axis of the quill. The two large gears are driven independently by corresponding driving motors, respectively, under control of an NC device. Each of the large gears engages with several small gears to rotate a driving cam for causing the tools to move between the advanced position and the retreated position so that the two tools can be operated simultaneously.
(2) JP-B2-4-74101 discloses a torsion spring manufacturing apparatus by which a torsion spring is formed by introducing a wire into a gap between a winding tool and a claw provided on the outer circumference of the winding tool by a predetermined length and axially moving the winding tool while rotating around the axis. The apparatus has feeding rollers for feeding a wire to the winding tool and is controlled so that a wire feeding speed by the feeding rollers is in conformity with a wire Winding speed by the winding tool.
(3) JP-B2-6-2296 discloses a method and a device of forming a torsion coil spring by moving a forming tool between an advanced position and a retreated position axially with respect to a quill, rotating the forming tool around the axis of the quill, and causing a wire fed out through the quill proximate to a distal end face of the forming tool. In the apparatus, two large gears, one for advancing and retreating the forming tools and another one for rotating the forming tool, are arranged in parallel to each other so as to be rotatable around an axial line intersecting with the axis of the quill. The two large gears are driven by servomotors, respectively, under a command of an NC device. Each of the large gears engage with several small gears.
(4) JP-A-8-174120 discloses a wire forming apparatus in which a plurality of forming tool units are disposed on a circular table which has a surface perpendicular to a feeding direction of a wire fed out from a wire feeding guide, the forming tools being radially slidable with respect to the circular table. In the apparatus, at least one of the forming tool units is provided with a first motor for driving a cam which operates a slider carrying the forming tool unit, a tool including a pair of projections between which wire is fed, and a second motor which rotates the tool.
Each of the spring forming apparatuses disclosed in JP-B2-4-734 and JP-B2-6-2296 is designed such that a single forming tool axially moves with respect to the quill and rotates around the forward end of the quill. A wire is bent by causing the forming tool to abut the wire after rotating the forming tool. Thus, the spring forming apparatuses have not only a disadvantage that wire bending radius is restricted to a definite value but also a problem of a slow forming speed and a low productivity because of the single forming tool.
Further, the torsion spring manufacturing device disclosed in JP-B2-6-74101 is designed to perform coiling working only for a coiled portion of the torsion coil spring, thus has a problem that it is not capable of easily performing bending or curling for a hook portion of the coil torsion spring.
Furthermore, the wire forming apparatus disclosed in JP-A-8-174120, in which the first and the second motors are provided to each of the plurality of forming tool units to move the tool between the advanced position and the retreated position and to rotate the same, has a problem that, for example, according to an embodiment shown in FIG. 1, it includes shafts to be controlled along as many as eleven axes and a complicated control program for the NC device is required. In addition, the NC device must have a large control capacity and a driving motor is needed for each of the forming tool units, thereby posing a problem that the wire forming apparatus is complicated and requires an expensive manufacturing cost.